Close the garage door fully
Pull the emergency release cord toward the opener to disengage it
Manually move the door until it is aligned and seated properly
Check that the trolley is in the correct position
Pull the emergency release cord again to reconnect the trolley
Run the opener until the trolley clicks back into place
Test the door using the wall button or remote
If the door does not reengage, inspect the track, trolley, and release mechanism
Contact a garage door technician if the opener still will not reconnect